Immunosuppressive drugs affect high-mannose/hybrid N-glycans on human allostimulated leukocytes.

Ewa Pocheć,Katarzyna Bocian,Grażyna Korczak-Kowalska,Marta Ząbczyńska,Anna Lityńska

doi:10.1155/2015/324980

Ewa Pocheć, Katarzyna Bocian + Show 3 more

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https://doi.org/10.1155/2015/324980

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Abstract

N-glycosylation plays an important role in the majority of physiological and pathological processes occurring in the immune system. Alteration of the type and abundance of glycans is an element of lymphocyte differentiation; it is also common in the development of immune-mediated inflammatory diseases. The N-glycosylation process is very sensitive to different environmental agents, among them the pharmacological environment of immunosuppressive drugs. Some results show that high-mannose oligosaccharides have the ability to suppress different stages of the immune response. We evaluated the effects of cyclosporin A (CsA) and rapamycin (Rapa) on high-mannose/hybrid-type glycosylation in human leukocytes activated in a two-way mixed leukocyte reaction (MLR). CsA significantly reduced the number of leukocytes covered by high-mannose/hybrid N-glycans, and the synergistic action of CsA and Rapa led to an increase of these structures on the remaining leukocytes. This is the first study indicating that β1 and β3 integrins bearing high-mannose/hybrid structures are affected by Rapa and CsA. Rapa taken separately and together with CsA changed the expression of β1 and β3 integrins and, by regulating the protein amount, increased the oligomannose/hybrid-type N-glycosylation on the leukocyte surface. We suggest that the changes in the glycosylation profile of leukocytes may promote the development of tolerance in transplantation.

Highlights

Most cell surface and secreted proteins in the immune system are N-glycosylated [1,2,3,4]
cyclosporin A (CsA) was responsible for removal of high-mannose/hybrid N-glycans from the surface of over 60% of the leukocytes, but the synergistic effect of both immunosuppressive drugs markedly increased the amount of oligomannose/hybrid-type N-glycans on the remaining cells
We observed higher intensity of the β1 subunit in mixed leukocyte reaction (MLR) treated with Rapa and the combination of both drugs. These results indicate that high-mannose/hybrid-type glycosylation did not change on a single β integrin molecule but that the increased binding of Galanthus nivalis lectin (GNA) resulted from enhancement of β integrin expression (Figures 3 and 4) and that it contributed to the overall increase of high-mannose/hybrid-type glycans on the cell surface in the presence of CsA and Rapa (Figure 1)

Summary

Introduction

Most cell surface and secreted proteins in the immune system are N-glycosylated [1,2,3,4]. N-glycans added to the special protein sequence (Asn-X-Ser/Thr) during the posttranslational process form a large and important part of glycoprotein molecules; the oligosaccharide component reaches up to even 50% of glycoprotein molecular mass [5]. High-mannose glycans have been considered to be incomplete products of the N-glycosylation synthesis pathway, evolutionarily older than complex-type structures. They are thought to be typical for simpler organisms like yeast or fungi [5, 7, 8], but some studies have shown that these oligosaccharide structures are abundant in mammalian cells and are no less important than completely processed complex-type sugar chains [9, 10]. Other work established that mannoserich oligosaccharides can suppress the immune response [13], ligand binding [14], and intracellular signal transduction [15]

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